在Lua中使用IUP获取输入

require "iuplua"
require "iupluagl"
require "luagl"

paddle = {x = -0.9, y = 0.2}

function drawPaddle(x, y)
    gl.Begin(gl.QUADS)
    gl.Color(0.0, 0.5, 0.0)

    gl.Vertex(x, y)
    gl.Vertex(x + 0.1, y)
    gl.Vertex(x + 0.1, y - 0.4)
    gl.Vertex(x, y - 0.4)
end

canvas = iup.glcanvas{buffer = "DOUBLE", rastersize = "300x300"}

function canvas:action(x, y)
    iup.GLMakeCurrent(self)
    gl.ClearColor(0.0, 0.0, 0.0, 0.0)
    gl.Clear(gl.COLOR_BUFFER_BIT)
    gl.Clear(gl.DEPTH_BUFFER_BIT)

    gl.MatrixMode(gl.PROJECTION)
    gl.Viewport(0, 0, 300, 300)
    gl.LoadIdentity()

    drawPaddle(paddle.x, paddle.y)

    gl.End()
    iup.GLSwapBuffers(self)
end

window = iup.dialog{canvas, title = "Soon to be Pong"}

function canvas:k_any(c)
    if c == iup.K_q then
        return iup.CLOSE
    elseif c == iup.K_w then
        paddle.y = paddle.y + 0.02
        return iup.CONTINUE
    else
        return iup.DEFAULT
    end
end

window:show()

iup.MainLoop()

canvas:k_any() 当按下某个键时,它会被调用,但它没有响应,甚至对quit命令也没有响应。有什么想法吗?